Without wanting to sound hard-nosed about it, Mike and I tend to build tools that we want to use ourselves. Neither of us are big fans of threaded discussion boards, so our motivation to do it really well would probably not be 100%, and as a result it would likely not be developed to the exacting and meticulous standards that we apply for the rest of the features. As a result, it's probably best to concentrate solely on what we do use and make it as good as possible, which means that as Mike said, I would not expect to see threaded mode appear as an option in XenForo any time soon.
Don't worry Kier, you don't sound harsh. From my own experience, the last time I saw a forum using threaded mode was about 2 years ago. It's quite difficult to keep a track of as well :/. Most modern forums opt for the standard view.
Most forums I am members of have the admins feel the same way about their sites. They make the site they way they want it, which makes for a content admin/owner, which makes everyone else that is interested in the forums topics more content. As opposed to trying to be all things to all people which pleases no one.
Suggestion. Possibly just a quick note in the title in threads like 'no thanks' so people know what the status is. Then if people feel like discussing things anyway at least they know where they stand.
When I turned it off on my own forums a year or so ago, I had a handful of members who asked where it went... not exactly enough interest from a user viewpoint either it seems. Not even worth while to run the extra queries for the minority who used it.
I can certainly understand and respect that XenForo devs do not want to add all the various kludges necessary to get Threaded mode working on top of their current code.
I think the poor adoption of threaded mode on vBulletin was attributable to it NOT being SlashDot. It was a pretty hobbled Threaded experience. I think we would have seen the threaded mode of vBulletin take off on certain boards if it displayed posts as a tree, rather than a threaded index on top of the old postbit. More importantly, I think a lot of people wanted to see threading for the community moderation aspect. If posts can be voted up and down, the community can self-police garbage/spam/nonsense posts and promote/bump useful stuff.
So I don't think the statement "nobody wants threaded mode" is really accurate. Nobody wanted the threaded mode as implemented in vBulletin. I realize that your software almost has to be built from the ground up to support this type of post system. XenForo may be so modular that this can be added as a content type by the third party community. If XenForo had a SlashDot-like way of sheperding conversations, they may be able to pick up dozens of communities using outdated, proprietary software.